Solar cells are manufactured in high volume using high throughput production methods. In high volume production solar cell metallization paste can be screen-printed at a rate of 3,500 wafers/hour. To reduce costs and improve solar cell performance it is desirable that the dimensions of front side electrodes be reduced. In high volume production, front side electrodes are typically fabricated by screen printing a metallization paste through a fine wire mesh. It is challenging to achieve integral fine-line front-side grid metallization having an aspect ratio greater than about 0.4 without discontinuities when printing metallization pastes through screens having openings less than 38 μm. Currently, screen openings can be around 34 μm. Line discontinuity can occur when the paste passes through the screen openings in the wire mesh, and the percent open area is smaller than the emulsion pattern of the gridline. The intersecting wires that form the printing mesh can also result in an interference or ‘necking’ pattern of the screen-printed gridlines that may show intervals of narrow widths that lead to increased gridline resistance. Also, if the paste is not well designed, the width of the printed gridlines can be up to 50% wider than the screen opening.
To provide an economical process for manufacturing solar cell gridlines, there is a need for thick-film metallization pastes that can be screen-printed through fine mesh screens at high speeds such as greater than 200 mm/sec, greater than 300 mm/sec, or greater than 350 mm/sec to provide conductive grids with small feature dimensions and high aspect ratios, and that exhibit low resistivity, high adhesion strength to the semiconductor substrate, and excellent solderability.